1. Field of the Invention
The present invention relates to a vibration reduction device for reducing nonlinear vibrations of the optical axis in an image taking optical system of an image taking apparatus.
2. Related Background Art
Conventionally, an AF device is popularly equipped in an image taking apparatus represented by a camera, and it is also proposed to add a vibration reduction device for reducing vibrations caused by camera shake to the image taking apparatus.
The vibration reduction device is built in the image taking apparatus, detects angular variations of the optical axis due to, e.g., camera shake, and corrects the image to be taken on the basis of the detection result. For example, Japanese Laid-Open Patent Application No. 2-66535 discloses a vibration reduction device applied to a single-element lens optical system, and Japanese Laid-Open Patent Application No. 2-183217 discloses an example wherein the image to be taken is corrected by moving some components of an image taking optical system in an inner-focus type telescopic lens.
In such vibration reduction devices, the moving amount of a vibration reduction mechanism is calculated on the basis of the detection result of the vibration amount by an appropriate means, and the vibration reduction device is moved on the basis of the calculation result. For this reason, a time lag is generated between the detection timing of the vibration amount and the calculation end timing. Hence, the vibration amount can be reduced to some extent, but such reduction operation always results in insufficient reduction.
In view of this problem, in recent years, means for minimizing the time lag have been proposed. For example, Japanese Laid-Open Patent Application No. 3-65935 proposes an invention in which an accelerometer is arranged in a vibration reduction optical system, and a calculation result after an elapse of (calculation time+response time) from the acceleration detection timing as the start point is predicted, and describes that fuzzy reasoning is used for attaining high-speed calculations.
On the other hand, Japanese Laid-Open Patent Application No. 5-40291 proposes an invention in which prediction calculations are performed on the basis of vibration reduction optical system movement data and vibration change amount data at a plurality of timings separated by given intervals so as to obtain vibration reduction data at the drive timing of a vibration reduction optical system, and vibration reduction is effectively performed in correspondence with the obtained data.
The prior art proposed by Japanese Laid-Open Patent Application Nos. 3-65935, 5-40291, and the like perform short-term prediction of vibrations under the assumption that the generated vibrations have some linearity.
In practice, however, vibrations are generated associated with the image taking apparatus holding operation of a photographer, and are nonlinear. For this reason, the prediction precision of vibration reduction is low even in short-term prediction, resulting in low vibration reduction precision.
In the prior art, the detection timing of vibration information such as an acceleration is used as the start point, and calculations are performed after this detection so as to predict vibrations. For this reason, the time required for calculations is indispensable, and a certain time lag cannot be eliminated. From this point of view as well, the prediction precision of vibration reduction is low.